Preparation method of carbon-ceramic composite material

Abstract

The invention discloses a preparation method of a carbon-ceramic composite material, which comprises the following steps: S1, carbon fiber modification treatment: firstly, depositing carbon nanotubes on the surface of short carbon fibers to form an intermediate layer, and constructing a secondary coarse structure; a chemical vapor deposition method is adopted, methane and hydrogen are introduced, the temperature is adjusted, nucleation is carried out on the surface of the carbon nano tube, and a graphene layer grows on the surface of the carbon nano tube; s2, infiltration and heat treatment: soaking the obtained modified short carbon fibers in a polycarbosilane solution through an easy impregnation method, carrying out pre-crosslinking, heating a sample to 150-350 DEG C in an air or inert atmosphere, and carrying out heat preservation for a period of time; the residual branched chain is further fractured and cross-linked to form an amorphous Si-C-O or Si-C network at 200-500 DEG C, the organic group is decomposed and transformed to disordered carbon and a primary SiC nanocluster at 500-1000 DEG C, atoms are rearranged and crystallized at 1000 DEG C to form nano SiC crystal grains, the nano SiC crystal grains are embedded into a carbon matrix, and the nano SiC crystal grains are transited to a pure SiC layer. According to the invention, the modified carbon fiber and the ceramic matrix can be better combined, and the layering risk is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon ceramic composite material preparation, and particularly relates to a preparation method of carbon ceramic composite material. BACKGROUND

[0002] There are many existing preparation processes of carbon ceramic materials. Generally, carbon fiber preforms are prepared first, and then carbon ceramic composite materials are prepared through multiple rounds of deposition such as chemical vapor deposition (CVI) or polymer impregnation pyrolysis (PIP). Another technology is to mix carbon fiber short fibers with ceramic materials and cold-press into a shape, and then prepare a ceramic composite material through chemical vapor deposition.

[0003] The mixing of carbon fibers and carbon ceramic materials prepared by the prior art causes inconsistent thermal expansion coefficients, which leads to material delamination in the later stage, and the performance of the material is reduced or even fails. In addition, the deposition process lasts for more than 100 hours, the preparation cycle is too long, and the economic cost is too high. Therefore, the present application provides a preparation method of carbon ceramic composite material. SUMMARY

[0004] The present application aims to provide a preparation method of carbon ceramic composite material to solve the problems in the prior art.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a preparation method of carbon ceramic composite material, comprising the following steps:

[0006] S1, carbon fiber modification treatment: first, deposit carbon nanotubes on the surface of chopped carbon fibers to form an intermediate layer and build a secondary rough structure; then, use chemical vapor deposition method, pass in methane and hydrogen and adjust the temperature to nucleate and grow a graphene layer on the surface of the carbon nanotubes;

[0007] S2, impregnation and heat treatment: the modified chopped carbon fibers obtained are soaked in a polycarbosilane solution by an easy impregnation method, pre-crosslinked, heated to 150-350 DEG C in air or inert atmosphere, and kept for a period of time; at 200-500 DEG C, residual branched chains are further broken and crosslinked into amorphous Si-C-O or Si-C network, at 500-1000 DEG C, organic groups are decomposed and converted to disordered carbon and primary SiC nanoclusters, and at 1000 DEG C or above, atomic rearrangement crystallization forms nano-SiC grains embedded in the carbon matrix, and transitions to a pure SiC layer; the general temperature is not more than 1400 DEG C, the heating rate is slow, 1-5 DEG C / min, and the temperature is kept for 2-5 hours;

[0008] S3, compression molding: the treated carbon fiber is immersed in a silicon carbide ceramic solution, a sintering aid Al2O3 is added, and under the protection of inert gas, one-time compression molding is carried out at a high temperature of 1000-1500 DEG C and a high pressure of 10-40 MPa; finally, heat treatment is carried out at a temperature of 1600-2200 DEG C, so as to promote the growth of SiC crystal grains, improve the crystallinity and material performance, and keep for 5-10 h, so as to obtain a carbon-ceramic composite material.

[0009] Preferably, in S1, the length of the chopped carbon fiber is 0.1-5 mm.

[0010] Preferably, in S1, the carbon fiber is first subjected to surface cleaning and activation, the sizing agent is removed, and then surface treatment is carried out to increase the surface activity; carbon nanotubes are first deposited, and then graphene is made on the basis of the carbon nanotubes.

[0011] When the carbon nanotubes are deposited, a transition metal-based catalyst is used, acetylene is used as a carbon source, argon is used as a protective gas, the temperature is 600-900 DEG C, and the deposition time is 1-10 h.

[0012] When the graphene layer is grown, copper foil is used as a catalyst, the temperature is controlled at 800-1200 DEG C under normal pressure, the volume ratio of methane to hydrogen is 1:5-1:20, and the deposition time is 1-10 h.

[0013] Preferably, in S2, the temperature is raised to 200-400 DEG C at a rate of 5-10 DEG C / min in the low-temperature stage, and kept for 2-4 h; the temperature is raised to 600-800 DEG C at a rate of 10-15 DEG C / min in the medium-temperature stage, and kept for 3-5 h; and the temperature is raised to 1000-1200 DEG C at a rate of 15-20 DEG C / min in the high-temperature stage, and kept for 4-6 h.

[0014] Preferably, in S2, the mass concentration of the polycarbosilane solution is 10%-30%, and the immersion time is 5-10 h.

[0015] Preferably, in S3, the addition amount of the sintering aid Al2O3 is 1%-5% of the mass of the silicon carbide ceramic solution.

[0016] Preferably, in S3, the immersion time is 2-4 h, and the pressure holding time of the compression molding is 1-3 h.

[0017] Preferably, the inert atmosphere or inert gas is at least one of nitrogen and argon.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] 1. The modified carbon fiber and the ceramic base can be better combined, and the delamination risk is reduced.

[0020] 2. The short-cut fibers are distributed in a three-dimensional random pattern. This structure makes it less prone to delamination or cracking like continuous fiber laminates when faced with rapid temperature changes, resulting in better thermal shock resistance.

[0021] 3. One-time molding greatly shortens the process time, improves production efficiency, enables near-size molding, and reduces production costs. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0023] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0025] Please see Figure 1 In this embodiment of the invention, a method for preparing a carbon-ceramic composite material includes the following steps:

[0026] S1. Carbon fiber modification treatment: First, carbon nanotubes are deposited on the surface of short-cut carbon fibers to form an intermediate layer and construct a secondary rough structure; then, methane and hydrogen are introduced and the temperature is adjusted by chemical vapor deposition to nucleate and grow a graphene layer on the surface of carbon nanotubes.

[0027] S2. Impregnation and Heat Treatment: The obtained modified short-cut carbon fibers are impregnated in a polycarbosilane solution using an easy impregnation method to pre-crosslink. The sample is then heated to 150℃-350℃ in air or an inert atmosphere and held for a period of time. At 200-500℃, the residual branches further break and crosslink into amorphous Si-CO or Si-C networks. At 500-1000℃, the organic groups decompose and transform into disordered carbon and nascent SiC nanoclusters. After 1000℃, atoms rearrange and crystallize to form nano-SiC grains embedded in the carbon matrix and transition to a pure SiC layer. Generally, the temperature does not exceed 1400℃, the heating rate should be slow (1-5℃ / min), and the holding time should be 2-5 hours.

[0028] S3, molding: the treated carbon fiber is immersed in a silicon carbide ceramic solution, Al2O3 is added as a sintering aid, and under the protection of inert gas, one-time molding is carried out at a high temperature of 1000-1500 DEG C and a high pressure of 10-40 MPa. Finally, heat treatment is carried out at a temperature of 1600-2200 DEG C to promote SiC grain growth, improve crystallinity and material performance, and then heat preservation for 5-10 h to obtain a carbon-ceramic composite material. Under high pressure conditions, the internal pores of the material are further compressed, the ceramic base is tightly combined with the carbon fiber, forming a high-density composite material, and avoiding the performance decline caused by loose structure.

[0029] In the S1, the length of the chopped carbon fiber is 0.1-5 mm, and the chopped fiber is distributed in three dimensions in a random direction, which can disperse the local stress caused by temperature change and avoid the problem of easy cracking of the continuous fiber laminated plate, thereby improving the thermal shock resistance of the material.

[0030] In the S1, the carbon fiber is first subjected to surface cleaning and activation, the sizing agent is removed, and the surface is then treated to increase the surface activity. Carbon nanotubes are deposited first, and then graphene is made on the basis of the carbon nanotubes. When growing the graphene layer, copper foil is used as a catalyst, and under normal pressure, the temperature is controlled at 800-1200 DEG C. The graphene is grown on the surface of the carbon nanotube, and the graphene has excellent flexibility and thermal conductivity, which can buffer the stress difference between the carbon fiber and the ceramic base when the temperature changes, thereby reducing the risk of delamination. The volume ratio of methane to hydrogen is 1:5-1:20, and the deposition time is 1-10 h.

[0031] In the S1, when depositing the carbon nanotubes, a chemical vapor deposition method is used, a transition metal-based catalyst is used, acetylene is used as a carbon source, argon is used as a protective gas, the temperature is 600-900 DEG C, and the deposition time is 1-10 h.

[0032] In the S2, in the low-temperature stage, the temperature is raised to 200-400 DEG C at a rate of 5-10 DEG C / min, and the temperature is kept for 2-4 h. The polycarbosilane undergoes crosslinking reaction to form amorphous Si-C-O or Si-C network, which preliminarily fixes the carbon fiber to prevent fiber displacement during subsequent high-temperature treatment, and at the same time, low-molecular volatile substances are discharged to avoid material cracking. In the medium-temperature stage, the temperature is raised to 600-800 DEG C at a rate of 10-15 DEG C / min, and the temperature is kept for 3-5 h. The organic groups (such as methyl and methylene) are decomposed, the polymer skeleton is converted to disordered carbon and primary SiC nanoclusters, and the transition from organic phase to inorganic phase is completed to provide a core for subsequent SiC grain growth. In the high-temperature stage, the temperature is raised to 1000-1200 DEG C at a rate of 15-20 DEG C / min, and the temperature is kept for 4-6 h. The atoms rearrange and crystallize, the primary SiC nanoclusters grow to form nano-SiC grains, which are embedded in the carbon matrix, and at the same time, gradually transition to a pure SiC layer.

[0033] In the S2, the mass concentration of the polycarbosilane solution is 10%-30%, the impregnation time is 5-10h, the impregnation process can fill the small gaps of the secondary rough structure on the surface of the carbon fiber, reduce the interface holes, avoid the stress concentration caused by the holes in the subsequent forming, and improve the material density.

[0034] In the S3, the addition amount of the sintering aid Al2O3 is 1%-5% of the mass of the silicon carbide ceramic solution, the sintering temperature of the SiC ceramic is reduced, the volatilization loss of the material at high temperature is reduced, the uniform growth of the SiC grains is promoted, the abnormal growth of the grains is inhibited, and the performance fluctuation caused by the uneven grain size is avoided.

[0035] In the S3, the impregnation time is 2-4h, and the pressure holding time of the mold pressing forming is 1-3h.

[0036] The inert atmosphere or inert gas is at least one of nitrogen and argon, the inert gas avoids the oxidation of the carbon fiber and the carbon matrix during the heat treatment process, ensures the stable growth of the SiC grains, and prevents the performance deterioration of the material caused by oxidation.

[0037] The working principle of the application is that: first, carbon nanotubes are deposited on the surface of the chopped carbon fiber to form an intermediate layer and build a secondary rough structure; then, by using the chemical vapor deposition method, methane and hydrogen are introduced and the temperature is adjusted, the graphene layer is nucleated and grown on the surface of the carbon nanotube; the modified chopped carbon fiber obtained is soaked in a polycarbosilane solution by an easy impregnation method, and is pre-crosslinked, and the sample is heated to 150-350 DEG C in air or inert atmosphere and is kept for a period of time; at 200-500 DEG C, the residual branched chain is further broken and crosslinked into amorphous Si-C-O or Si-C network, at 500-1000 DEG C, the organic group is decomposed and is converted into disordered carbon and nascent SiC nanoclusters, and at 1000 DEG C or above, the atoms are rearranged to form nano-SiC grains embedded in the carbon matrix and transition to a pure SiC layer; the general temperature is not more than 1400 DEG C, the heating rate is slow, 1-5 DEG C / min, and the heat preservation time is 2-5 hours; the treated carbon fiber is impregnated in a silicon carbide ceramic solution, a sintering aid Al2O3 is added, and under the protection of inert gas, one-time mold pressing forming is carried out at a high temperature of 1000-1500 DEG C and a high pressure of 10-40 MPa, and finally heat treatment is carried out at a temperature of 1600-2200 DEG C, to promote the growth of SiC grains, improve the crystallinity and material performance, and keep for 5-10h, to obtain a carbon ceramic composite material.

[0038] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that the technical solutions described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalent ones. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a carbon-ceramic composite material, characterized in that, Includes the following steps: S1. Carbon fiber modification treatment: First, carbon nanotubes are deposited on the surface of short-cut carbon fibers to form an intermediate layer, thus constructing a secondary rough structure; Then, using chemical vapor deposition, methane and hydrogen are introduced and the temperature is adjusted to nucleate and grow a graphene layer on the surface of carbon nanotubes. S2. Impregnation and heat treatment: The obtained modified short-cut carbon fibers are impregnated in a polycarbosilane solution using an easy impregnation method to pre-crosslink. The sample is heated to 150℃-350℃ in air or an inert atmosphere and held for a period of time. At 200-500℃, the residual branches are further broken and crosslinked into an amorphous Si-CO or Si-C network. At 500-1000℃, the organic groups decompose and transform into disordered carbon and nascent SiC nanoclusters. After 1000℃, the atoms rearrange and crystallize to form nano-SiC grains embedded in the carbon matrix and transition to a pure SiC layer. The temperature does not exceed 1400℃, the heating rate is 1-5℃ / min, and the holding time is 2-5 hours. S3. Compression molding: The treated carbon fiber is impregnated in a silicon carbide ceramic solution, and sintering aid Al2O3 is added. Under inert gas protection, it is subjected to compression molding at a high temperature of 1000℃-1500℃ and a high pressure of 10-40MPa. Finally, it is heat-treated at a temperature of 1600-2200℃ to promote SiC grain growth, improve crystallinity and material properties, and then held at the temperature for 5-10 hours to obtain carbon-ceramic composite material.

2. The method for preparing a carbon-ceramic composite material according to claim 1, characterized in that, In S1, the length of the short-cut carbon fiber is 0.1-5mm.

3. The method for preparing a carbon-ceramic composite material according to claim 1, characterized in that, In step S1, the carbon fiber is first cleaned and activated to remove the sizing agent and then surface treated to increase surface activity; carbon nanotubes are first deposited, and then graphene is made on the basis of the carbon nanotubes. When depositing carbon nanotubes, a transition metal-based catalyst is used, acetylene is used as the carbon source, argon is used as the protective gas, the temperature is 600-900℃, and the deposition time is 1-10h. When growing graphene layers, copper foil is used as a catalyst, the temperature is controlled at 800-1200℃ under normal pressure, the volume ratio of methane to hydrogen is 1:5-1:20, and the deposition time is 1-10h.

4. The method for preparing a carbon-ceramic composite material according to claim 1, characterized in that, In step S2, the temperature is increased to 200-400℃ at a rate of 5-10℃ / min during the low-temperature stage and held for 2-4 hours; the temperature is increased to 600-800℃ at a rate of 10-15℃ / min during the medium-temperature stage and held for 3-5 hours; and the temperature is increased to 1000-1200℃ at a rate of 15-20℃ / min during the high-temperature stage and held for 4-6 hours.

5. The method for preparing a carbon-ceramic composite material according to claim 1, characterized in that, In S2, the mass concentration of the polycarbosilane solution is 10%-30%, and the impregnation time is 5-10 hours.

6. The method for preparing a carbon-ceramic composite material according to claim 1, characterized in that, In S3, the amount of sintering aid Al2O3 added is 1%-5% of the mass of the silicon carbide ceramic solution.

7. The method for preparing a carbon-ceramic composite material according to claim 1, characterized in that, In step S3, the impregnation time is 2-4 hours, and the pressure holding time for compression molding is 1-3 hours.

8. The method for preparing a carbon-ceramic composite material according to claim 1, characterized in that, The inert atmosphere or inert gas is at least one of nitrogen or argon.

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